1. Field of the Invention
This invention relates to a fastening for a bottom plate of a switchgear cabinet, wherein an edge of at least one bottom plate is placed on a support flange of a bottom frame of the switchgear cabinet and is clamped together with at least one tightening clamp, wherein the tightening clamp has two legs which are parallel with each other and are held on a connecting section, wherein the first leg grasps the support flange of the bottom from behind, and wherein the other leg holds a screw in a thread, which can be tightened against the edge of the bottom plate.
2. Description of Prior Art
Such a bottom plate fastening is known from German Patent Reference DE 44 46 223 C1. The bottom frame of the switchgear cabinet is assembled from four profiled sections. The profiled sections are essentially embodied in a U-shape, wherein two vertically projecting profiled sides are connected to a horizontal support section. The edges of the profiled sides are beveled. A horizontal support flange is thus created on the profiled section located in the interior, on which bottom plates can be laid flat. The edges of the bottom plates can be connected with the support flange with tightening clamps. The tightening clamps are designed as U-shaped components with two parallel legs.
The edge and the support flange are located between the two legs. One of the legs has a screw, by which the bottom plate can be clamped together with the support flange on the second leg.
It is one object of this invention to produce a fastening of the type mentioned at the outset, wherein the bottom plate and the bottom frame can be dependably placed on a same electrical level.
This object is achieved with a first leg supported by bezels and/or tips of contacting elements on the support flange, wherein the screw is in an electrically conducting contact with the edge of the bottom plate.
When the tightening clamp is tightened, the bezels and/or tips dig into the support flange. In particular, a layer of lacquer on the support flange can be penetrated, to assure electrical contact between the tightening clamp and the support flange. The electrically conducting connection with the bottom plate is produced via the screw. When screwed in, the screw contacts the bottom plate. Because of tightening of the screw, the screw rubs across the surface of the bottom plate and thus is able to create an assured electrical contact.
In accordance with a preferred embodiment of this invention, at least two contacting elements, which are embodied as tongues, are stamped out of the first leg and are bent in a direction toward the support flange. The ends of the tongues are cut off transversely with respect to their longitudinal sides, so that bezels are formed. A cost-effective production of the tightening clamps is possible with this simple step.
Stiffening of the tightening clamps is achieved if the connecting section has reinforcement ribs, which extend vertically in relation to the legs. Thus the connecting section is not bent when the screw is tightened.
Also, the reinforcement ribs extend past the edge areas formed between the connecting section. This simple step prevents the legs from being bent open when the tightening clamp is tightened. Large clamping forces can be transferred to the bottom plate and the support flange by such a rigid tightening clamp.
In another embodiment of this invention, the tightening clamp is formed in a U-shape from a stamped bent component, and the leg facing the bottom plate has a bulge-like thickened place into which the screw receptacle for the screw is cut. It is thus possible for the tightening clamp to be made of a relatively thin sheet metal material. A sufficient length of the screw thread is assured due to the thickening.
The front of the screw can have protrusions for an improved electrical contact between the bottom plate and the screw. These dig into the surface of the bottom plate when the screw is tightened.